As countries rapidly expand renewable energy generation, scientists and engineers across the world are developing a new generation of unconventional energy storage technologies that could transform how clean electricity is stored and used. While lithium-ion batteries continue to dominate the market, concerns over the availability of critical minerals, environmental impacts and long-term sustainability are prompting researchers to explore innovative alternatives ranging from molten salt and liquid air to sand and even human sweat.
The growing need for better storage solutions stems from the intermittent nature of renewable energy sources such as solar and wind. Electricity generated during periods of abundant sunshine or strong winds often exceeds immediate demand, making efficient storage essential to ensure uninterrupted power supply when weather conditions change. Around the world, several large-scale and experimental projects are now showcasing how different materials and technologies can address this challenge without relying heavily on conventional battery chemistry.
Among the most ambitious initiatives is a massive clean energy project in the United Arab Emirates, where authorities are integrating 5.2 gigawatts of solar generation with an enormous 19 gigawatt-hour battery storage system. Once fully operational, the project is expected to supply enough electricity to power nearly half a million homes throughout the night, making it one of the world’s largest renewable energy storage ventures.
In the United Kingdom, developers are advancing a radically different concept through “liquid air” technology. At a facility under construction in Greater Manchester, surplus renewable electricity is being used to cool air to extremely low temperatures, converting it into liquid form. The liquid air can then be stored for extended periods before being reheated to expand into gas, driving turbines that generate electricity whenever demand increases. Developers believe the technology could store energy for hours, days or even weeks while helping balance electricity grids increasingly dependent on renewable sources.
Meanwhile, researchers are harnessing the power of extreme heat rather than freezing temperatures. In Nevada, a solar thermal facility uses thousands of mirrors to concentrate sunlight and heat molten mixtures of potassium and sodium nitrate to temperatures exceeding 560 degrees Celsius. The stored heat remains available long after sunset and is later converted into electricity through steam turbines. Denmark is also investing in molten salt technology for industrial applications, with a large-scale project capable of storing renewable energy for up to two weeks before releasing it as high-temperature steam for manufacturing processes.
Another unconventional solution has emerged in Finland, where engineers are using thousands of tonnes of crushed soapstone as a giant thermal battery. The heated sand stores renewable energy in the form of heat, supplying district heating to schools, libraries and other public buildings. During summer, the system can meet nearly a month’s heating demand, while in winter it provides sufficient energy for about a week, significantly reducing dependence on fossil fuels and biomass.
Innovation is not limited to large infrastructure projects. At the opposite end of the scale, scientists at Tokyo University of Science are investigating how human sweat can become a practical energy source for wearable electronics. They have developed a thin skin patch equipped with enzymatic biofuel cells that convert lactate found in sweat into electricity. The technology could eventually eliminate the need for miniature rechargeable batteries in wearable health monitors and fitness devices by generating power continuously as people go about their daily activities.
Researchers in the United States are also working on ultra-small batteries designed to power electronic tags for tracking young fish species, demonstrating that future energy storage solutions may be tailored to highly specialised applications beyond household electricity and electric vehicles.
Experts believe these diverse technologies could play complementary roles in the global transition to clean energy. Unlike conventional lithium-ion batteries, many of these alternatives rely on abundant materials, offer longer operational lifespans and can be recycled more easily at the end of their service lives. Although many remain in developmental or early deployment stages, they represent promising pathways to overcoming one of renewable energy’s biggest challenges—storing clean electricity efficiently, sustainably and at every scale, from powering national grids to running wearable devices.
